Table 1.
Demographic characteristics of juvenile idiopathic arthritis (JIA) cases and playmate-matched controls.*
| Playmate-matched Control** (n=138) | Case** (n=225) | |
|---|---|---|
| Female | 78 (56.5) | 159 (70.7) |
| Age at time of survey (years) mean (sd, IQR) | 10.7 (4.1, 8 – 14) | 11.1 (4.1, 8 – 15) |
| Duration of diagnosis (years) mean (sd, IQR) | 5.1 (3.7, 2–7.5) | |
| Race | ||
| Caucasian | 110 (79.7) | 191 (84.9) |
| Other (Asian, African-American, Native American) | 5 (3.6) | 18 (8) |
| Multiracial | 18 (13) | 16 (7.1) |
| Ethnicity | ||
| Hispanic or Latino | 11 (8) | 22 (9.8) |
| Annual household income ($/year) | ||
| < 25,000 | 4 (2.9) | 15 (6.7) |
| 25,000–49,999 | 11 (8) | 31 (13.8) |
| 50,000–74,999 | 29 (21) | 43 (19.1) |
| 75,000–99,999 | 24 (17.4) | 26 (11.6) |
| 100,000–150,000 | 26 (18.8) | 52 (23.1) |
| >150,000 | 26 (18.8) | 32 (14.2) |
| Perinatal Characteristics | ||
| Birth Weight (grams) | ||
| Low (<2500) | 7 (5.1) | 14 (6.2) |
| Normal (2500–3999) | 94 (68.1) | 166 (73.8) |
| High (≥4000) | 24 (17.4) | 31 (13.8) |
| Mode of delivery | ||
| Vaginal | 89 (64.5) | 147 (65.3) |
| C-section | 44 (31.9) | 57 (25.3) |
| Forceps/ Vacuum | 1 (0.7) | 14 (6.2) |
| Gestational age (weeks) | ||
| Pre-term (< 37) | 11 (8) | 32 (14.2) |
| Term (37–41) | 88 (63.8) | 151 (67.1) |
| Post-term (≥42) | 22 (15.9) | 32 (14.2) |
| Place of delivery | ||
| Hospital or Birthing Center | 120 (87) | 185 (82.2) |
| Home | 0 (0) | 5 (2.2) |
| Body Mass Index (kg/m2) | ||
| Underweight (<18.5) | 50 (36.2) | 97 (43.1) |
| Normal (18.5–<25) | 54 (39.1) | 90 (40) |
| Overweight (25–<30) | 6 (4.3) | 24 (10.7) |
| Obese (≥ 30) | 3 (2.2) | 12 (5.3) |
| Smoking | ||
| Household Smoking | 25 (18.1) | 41 (18.2) |
| Maternal prenatal smoking | 6 (4.3) | 11 (4.9) |
| 1–9 cigarettes/day | 2 (1.4) | 7 (3.1) |
| 10–19 cigarettes/day | 3 (2.2) | 3 (1.3) |
| 20+ cigarettes/day | 0 (0) | 1 (0.4) |
| Duration prenatal smoking (months) | (n=5) | (n=8) |
| mean (sd) | 7.2 (3.0) | 5.3 (3.0) |
| median (IQR) | 9 (5, 9) | 5 (3, 8) |
| Maternal smoking | 9 (6.5) | 25 (11.1) |
| Smoked inside house | 2 (1.4) | 1 (0.4) |
| Smoked outside house | 7 (5.1) | 24 (10.7) |
| 1–9 cigarettes/day | 0 (0) | 8 (3.6) |
| 10–19 cigarettes/day | 3 (2.2) | 9 (4) |
| 20+ cigarettes/day | 3 (2.2) | 4 (1.8) |
| Paternal smoking | 17 (12.3) | 26 (11.6) |
| Smoked inside house | 2 (1.4) | 2 (0.9) |
| Smoked outside house | 15 (10.9) | 24 (10.7) |
| 1–9 cigarettes/day | 5 (3.6) | 9 (4) |
| 10–19 cigarettes/day | 3 (2.2) | 5 (2.2) |
| 20+ cigarettes/day | 5 (3.6) | 7 (3.1) |
| Relative smoking | 6 (4.3) | 13 (5.8) |
| Smoked inside house | 1 (0.7) | 1 (0.4) |
| Smoked outside house | 5 (3.6) | 12 (5.3) |
| 1–9 cigarettes/day | 4 (2.9) | 5 (2.2) |
| 10–19 cigarettes/day | 0 (0) | 1 (0.4) |
| 20+ cigarettes/day | 1 (0.7) | 1 (0.4) |
| Breastfed | 112 (81.2) | 184 (81.8) |
| Duration of breastfeeding (months) | ||
| <6 | 26 (18.8) | 47 (20.9) |
| 6–12 | 29 (21) | 53 (23.6) |
| 12 – 24 | 48 (34.8) | 57 (25.3) |
| ≥24 | 5 (3.6) | 16 (7.1) |
| Cow’s milk introduction*** | ||
| < 1 year of age | 11 (8) | 30 (13.3) |
| ≥1 year of age | 100 (72.5) | 176 (78.2) |
| Early life infections | ||
| Hospitalization for infection <1 year | 8 (5.8) | 27 (12) |
| Daycare attendance < 6 years | 67 (48.6) | 120 (53.3) |
| Household pets | 99 (71.7) | 159 (70.7) |
| Dog | 46 (33.3) | 63 (28) |
| Cat | 20 (14.5) | 38 (16.9) |
| Other | 6 (4.3) | 4 (1.8) |
| More than one pet | 27 (19.6) | 53 (23.6) |
| At least one dog in the household | 73 (52.9) | 112 (49.8) |
| At least one cat in the household | 41 (29.7) | 87 (38.7) |
| At least one other type of pet | 15 (10.9) | 19 (8.4) |
| Birth Order | ||
| First | 59 (42.8) | 94 (41.8) |
| Second | 53 (38.4) | 83 (36.9) |
| Third or more | 26 (18.8) | 45 (20) |
| Stressors | ||
| None | 79 (57.2) | 132 (58.7) |
| Any one stressor | 38 (27.5) | 58 (25.8) |
| Multiple stressors | 18 (13) | 33 (14.7) |
| Type of stressor | ||
| Death in family | 21 (15.2) | 17 (7.6) |
| Divorce in family | 5 (3.6) | 21 (9.3) |
| Move in family | 23 (16.7) | 49 (21.8) |
| New school | 26 (18.8) | 38 (16.9) |
| Unemployment | 7 (5.1) | 8 (3.6) |
| Other characteristics | ||
| Maternal age (years) | ||
| <20 | 0 (0) | 2 (0.9) |
| 20–34 | 49 (35.5) | 107 (47.6) |
| 35+ | 86 (62.3) | 111 (49.3) |
| Paternal age (years) | ||
| <20 | 1 (0.7) | 1 (0.4) |
| 20–34 | 40 (29) | 80 (35.6) |
| 35+ | 93 (67.4) | 126 (56) |
| Mother’s marital status | ||
| Married or Living partner | 126 (91.3) | 192 (85.3) |
| Single/Separated/Divorced/Widowed | 12 (8.7) | 32 (14.2) |
| Residential area | ||
| Urban | 93 (67.4) | 135 (60) |
| Rural | 44 (31.9) | 87 (38.7) |
| Moved residence | 54 (39.1) | 105 (46.7) |
| Type of residential move | ||
| Urban to Urban | 24 (17.4) | 49 (21.8) |
| Urban to Rural | 4 (2.9) | 10 (4.4) |
| Rural to Urban | 3 (2.2) | 8 (3.6) |
| Rural to Rural | 11 (8) | 17 (7.6) |
*
Values are frequency (percentage) unless otherwise indicated.
**
Some variables may not add up to totals due to missing data.
***
Three JIA cases never introduced cow’s milk into diet.
Abbreviations: sd: standard deviation, IQR: interquartile range